Statistical modelling and analysis of big data on pedestrian movement

This work follows a long line of studies and empirical investigations in Space Syntax research, that, in general, try to conceptualise, describe and quantify the relation between physical space and human agency. How many people share public space is known to affect many socio-economic processes in cities, such as segregation, vitality and local commercial markets. Observing and measuring pedestrian movement through surveys, as well as statistically analysing it have been at the core of diverse investigations not least in the field of Space Syntax, not only a means to validate and measure the dependence of pedestrian movement on spatial configuration, but also as a means to forecast and predict pedestrian flows. However, these studies do not necessarily provide us with comparable, let alone generalisable findings that can lead to generalisable propositions. They remain in most cases specific investigations of particular cities, neighbourhoods or types of areas (e.g. city centres). Another issue, as will be elaborated in this paper, is that the typical statistical methods used, such as multivariate regression models, are not always the optimal or even suitable for modelling pedestrian movement, typically measured in pedestrian counts.\ua0This paper aims therefore, to directly address three methodological challenges: first, construction of comparable GIS-models; second, gathering large scale pedestrian data; third, applying advanced statistical modelling suitable for pedestrian data.The ultimate goal is to estimate the impact of spatial form on urban life in a way that is methodologically sound and can provide robust results that can be generalisable, and allows us to speak of the relation between spatial form and pedestrian movement in a way that is not specific to a certain area, or types of areas or streets, or even to a specific city. \ua0The results show, first, high and consistent correlations between spatial form and pedestrian movement in a study of unprecedented size that comprises three cities, including a large range of neighbourhoods of varying morphological types, from villa areas to urban cores, and offer convincing proof that the tested morphological variables have a strong impact on the spatial distribution of pedestrian flows in cities. Second, the study shows that the model with all explanatory variables has the highest explanatory power and the best model fit where Angular integration and Accessible FSI are the explanatory variables with the largest effect on pedestrian movement, but others are significantly contributing to the predictive power of the model. Third, the study contributes to the advancement of the statistical modelling that is suitable for the specificities of the data used, proposing the use of a negative Binomial model instead of regression models, most common in the field

Coherent quantum dynamics of excitons in monolayer transition metal dichalcogenides

Transition metal dichalcogenides (TMDs) have garnered considerable interest in recent years owing to their layer thickness-dependent optoelectronic properties. In monolayer TMDs, the large carrier effective masses, strong quantum confinement, and reduced dielectric screening lead to pronounced exciton resonances with remarkably large binding energies and coupled spin and valley degrees of freedom (valley excitons). Coherent control of valley excitons for atomically thin optoelectronics and valleytronics requires understanding and quantifying sources of exciton decoherence. In this work, we reveal how exciton-exciton and exciton-phonon scattering influence the coherent quantum dynamics of valley excitons in monolayer TMDs, specifically tungsten diselenide (WSe2), using two-dimensional coherent spectroscopy. Excitation-density and temperature dependent measurements of the homogeneous linewidth (inversely proportional to the optical coherence time) reveal that exciton-exciton and exciton-phonon interactions are significantly stronger compared to quasi-2D quantum wells and 3D bulk materials. The residual homogeneous linewidth extrapolated to zero excitation density and temperature is 1:6 meV (equivalent to a coherence time of 0.4 ps), which is limited only by the population recombination lifetime in this sample. (c) (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use onl

K+ΛK^+\Lambda and K+Σ0K^+\Sigma^0 photoproduction with fine center-of-mass energy resolution

Measurements of $\gamma p \rightarrow K^{+} \Lambda$ and $\gamma p \rightarrow K^{+} \Sigma^0$ cross-sections have been obtained with the photon tagging facility and the Crystal Ball calorimeter at MAMI-C. The measurement uses a novel $K^+$ meson identification technique in which the weak decay products are characterized using the energy and timing characteristics of the energy deposit in the calorimeter, a method that has the potential to be applied at many other facilities. The fine center-of-mass energy ($W$) resolution and statistical accuracy of the new data results in a significant impact on partial wave analyses aiming to better establish the excitation spectrum of the nucleon. The new analyses disfavor a strong role for quark-diquark dynamics in the nucleon.Comment: 7 pages, 8 figure

Technomass and cooling demand in South America: a superlinear relationship?

The impact of the increasing technomass (TM) on cooling demand in buildings is explored for cities in South America. The entangled double nature of the building–environment interrelation in an urban context is analyzed. The research question is whether an increase in the building density produces a superlinear increase of energy consumption at the urban scale. Advanced spatially explicit quantitative methods are used to select representative samples of the urban environment and to quantify the volumes of TM in four South American cities. Principal component analysis is used to extract representative urban tissue categories. The Urban Weather Generator tool is used to produce the urban weather data used in building performance simulations. The results confirm the superlinear dependence of the total cooling consumption of each sample in relation to the existing TM in areas with high-rise buildings due to the combined primary and secondary effects, namely, the increase of the total energy needs and the increase of air temperature due to the urban heat island effect. The great significance of the second-order effect poses challenges to current assessments performed on the basis of consumption per m2. The use of the TM indicator can promote the development of climate-sensible urban planning

Should all adjunctive corticosteroid therapy be avoided in the management of hemodynamically stabile Staphylococcus aureus bacteremia?

The purpose of this study was to examine the prognostic impact of corticosteroids in hemodynamically stabile Staphylococcus aureus bacteremia (SAB). There were 361 hemodynamically stabile methicillin-sensitive SAB patients with prospective follow-up and grouping according to time-point, dose and indication for corticosteroid therapy. To enable analyses without external interfering corticosteroid therapy all patients with corticosteroid therapy equivalent to prednisone > 10 mg/day for >= 1 month prior to positive blood culture results were excluded. Twenty-five percent (92) of patients received corticosteroid therapy of which 11 % (40) had therapy initiated within 1 week (early initiation) and 9 % (31) had therapy initiated 2-4 weeks after (delayed initiation) positive blood culture. Twenty-one patients (6 %) had corticosteroid initiated after 4 weeks and were not included in the analyses. A total of 55 % (51/92) received a weekly prednisone dose > 100 mg. Patients with early initiated corticosteroid therapy had higher mortality compared to patients treated without corticosteroid therapy at 28 days (20 % vs. 7 %) (OR, 3.11; 95% CI, 1.27-7.65; p = 100 mg/week the negative prognostic impact on 28-day mortality was accentuated (HR 4.8, p = 0.001). Corticosteroid therapy initiation after 1 week of positive blood cultures had no independent prognostic impact. Early initiation of corticosteroid therapy may be associate to increased mortality in hemodynamically stabile SAB.Peer reviewe

Functional ANOVA modelling of pedestrian counts on streets in three European cities

The relation between pedestrian flows, the structure of the city and the street network is of central interest in urban research. However, studies of this have traditionally been based on small data sets and simplistic statistical methods. Because of a recent large-scale cross-country pedestrian survey, there is now enough data available to study this in greater detail than before, using modern statistical methods. We propose a functional ANOVA model to explain how the pedestrian flow for a street varies over the day based on its density type, describing the nearby buildings, and street type, describing its role in the city’s overall street network. The model is formulated and estimated in a Bayesian framework using hour-by-hour pedestrian counts from the three European cities, Amsterdam, London and Stockholm. To assess the predictive power of the model, which could be of interest when building new neighbourhoods, it is compared with four common methods from machine learning, including neural networks and random forests. The results indicate that this model works well but that there is room for improvement in capturing the variability in the data, especially between cities

Photoproduction of the omega meson on the proton near threshold

Publisher's version/PDFAn experimental study of [omega] photoproduction on the proton was conducted by using the Crystal Ball and TAPS multiphoton spectrometers together with the photon tagging facility at the Mainz Microtron MAMI. The [gamma] p [right arrow] [omega] p differential cross sections are measured from threshold to the incident-photon energy E[subscript gamma] = 1.40 GeV (W = 1.87 GeV for the center-of-mass energy) with 15-MeV binning in E[subscript gamma] and full production-angle coverage. The quality of the present data near threshold gives access to a variety of interesting physics aspects. As an example, an estimation of the [omega]N scattering length [alpha subscript omega]p is provided